Short wave broadcast antenna



April 16, 1940.

N. E. LINDENBLAD SHORT WAVE BROADCASTANTENNA Filed Oct. 8, 1938 2 Sheets-Sheet 1 INVENTOR. N/LS/EZL/NDENBLAD BY ATTORNEY.

April 16, 1940 N E. LINDENBLAD 2.197.051

SHORT WAVE BROADCAST ANTENNA Filed Oct. 8, 1938 2 Sheets-Sheet 2 A i I l a .9- 2 4 A EXREFERENCE I I A I 2 I:

PHASE REFERENCE r A LINE OR I l WAVE FRoNr I PHASE ,47' PHASE A7 REFERENCE I REFERENCE X1 L/NEXr-X LINE 21-2;

R: /./62 R: 1.0 e=.30 '43 e=90 ,4 A A 1 A? A2 0 4 i i PHASE 3 I i RE L 1 ENcE ILA/2 571M300 4 o 2 I4 32 #12; SIN. 60 A12 57M 60 k A SIM I E T2 PHASE A I RLEFERENQF fi A I INE I RNAsE Ar PHASE AT REFERENCE I REFERENCE X2 uNE Xg-Xg Z2 LINE Z2(Z2 A Q a N N A 32 INVENTOR.

N/LS E. LINDENBLA D BY m A TTORIY E Y.

Patented Apr. 16, 1940 n;

was

I v v ..2,i9.7,o51 snon'r wave BRQADCAST ANTENNA I I Nils El Lindenblad liort Jefferson, N; Y., assignor to Radio Corporation of America, a corporation of Delaware j 12Claims'.

- 1 Theipresentinvention relates to radio antennas and, moreparticularly; to short wave antennas capable 20f t giving a substantiallyuniform r'adi ation-towardv all points on the horizonlThe use .of very high frequency energy for radio communi cation is exceedingly desirable because of :the great distances? *covered' by: comparatively small amounts'ofenergyi' However, theregular use of shortwaves'for communication is seriously hanrdicappedby. the severe fading encountered, by phase distortion and echo effects produced by the signal travellingover the plurality ofpaths of different length due to the signal being reflected from .varied': refiecting' surfaces encountered. This is likewisetrue even at suchhigh frequencies that the Heaviside. layer ceasesuto function as a reflector orrefractonor "both; at such frequencies'buildingsiand. other structures then' act as reflectors. 1 r 1 w 1 My present;.- invention: reduces these. difficulties byztransmitting .a wave polarized in both hori- ;-zontal and'vertical planesinstead of ina single plane only; Depending .upon the amplitude and phase relationship betweenlthertwo components the resultant wave maybe either merely tilted or-itmay be rotary. If the, Wave peaks-of the .cularly polarized wave containing both horizontal and vertical polarized components Will, of .course,'give the advantagesof each. Y

My invention has as anobject the attainment of the foregoing advantages..- i

A further objectof my invention is to provide an antenna structure for radiating electro magnetic waves having avarying plane of polarization.

Another object of myinv ention'is to provide an antenna which radiates a radio wave With a varying plane of polarization having an intrinsic relationship to the frequency of the radiated waves. Still a further object of my inventionis to provide a short Wave antenna which is mechanically strong and is entirely electrically grounded as a protection against. lightning. v t

p The antenna of my invention comprisesa p111. rality of conductors arranged at the corners of an equilateral figure and having alternating ver- J1 Application October 8;

1938. Serial n 233,894 (01. 250-33) tical and horizontal half wave sections arranged spirally around the circumference of said figure;

In apreferred form of my invention the vertical conductors are arranged at the corners of'an equilateral triangle, since, as I have disclosed in my ccpending application No. 76,745, filed April 28, 1936, the triangular arrangement readily gives a uniform radiation in a horizontal planewhil'e other arrangements may not readily do so.

The following description is accompanied by d ravvingsin Which'fiigure -1 shows an embodiment or my invention,while Figures 2, 3, 4 and 5 are vector diagrams showingthe operation of my invention. In Figure 1 reference'numerals' l,'2

and? indicate the threeradiating conductorsv of -my invention'zwhich ar'e located'at the'corners of a horizontally disposed equilateral-triangle. Vertically 'upward from point I the-conductor extends a distance equal toa'half-the length of the-operatingi-wave as radiator ll. 'At "the top end of H and at right angles thereto, the conductor continues. as a horizontal. half waveradi- .aterlfiwhiclzi lies parallel to one side 0f"th6 equilateral triangle-"The conductor then extends 'up'Wardly'"as'rat l3 and continues :spirally around the antenna through: half' Wave radiating secill" 'ti'ons M; and iii. Conductors 2 and 3 at theother corners-0f .the'base triangle'similarly ad "vance .spirallyhupward around central mast 5. -At"voltage nodal points of each of the half wave sectionsfcori-ductin'gsupports 6 are attached. The other .endofeach of thesupports 6 is attached 'tothe mast Thecentralsupporting mast 5 is preferably censtructed of: a conducting material :vvhereby the entire antenna may be grounded as :a. protection against lightning strokes.

' By-reference toythe diagrams inFigures 2, 3, 4 and 5, itwill be seen=how the resultant radiation from. all" ofuthevertical members'becomes approximatelyQO degrees out: of phase with the re -sultant from all the horizontal members. The combinationofthesetwo resultants in space re- .sults in asubstantially circularly polarized field. Referringto Figure 2, which shows the efiect of the radiation from 3 of-the verticalmembers ll, .21 and SI; for instance, in alphase reference' line or wave front'parallel to aplane passing through members H ands! Theeifective radiation from each ofjwthe members H, Xi andjel is represented .in:Figure ;2 by the vectorsAi, A2 and A3. .yectors A zand As are in the samedirection and originate irom the sameplanethey add in direct phase relationship. The radiationrepresented by .vector Az,- by the timeit has advanced to the pha e re e e 11i X ;..X ..W i :p effective in Since a direction as shown by the vector diagram in the lower part of Figure 2. The resultant radiation is denoted by reference letter R and has an amplitude equal to 1.162 times the radiation from any individual vertical conductor. The'phase angle of the resultant as shown by the vector diagram is'approximately 20 degrees, 30 minutes. Similarly, the analysis of the radiation from the horizontal members I2, 22 and 32, due to the currents I, is shown in Figure 3. The same phase reference line is taken as in Figure 2. Here, it will be seen, the entire radiation from portion of the radiation from each of radiators i2 and 22, which is effective in that direction, is represented by the vectors A12sin.30 degrees and vector A22sin.30 degrees. These two vectors will add in phase and by the time their resultant has reached the phase reference line X2, X2 will be in a direction as shown by the vector diagram in the lower part of Figure 3. This resultant will combine with the radiation A32 to form the resultant R having an amplitude equal to 1.275 times the radiation from any individual conductor and at a relative phase angle of 51 degrees and 32 minutes.

From. a consideration of these two diagrams it will be seen that the time phase relationship between the radiation from the vertical members and the horizontal members is approximately '73 degrees in the particular reference line chosen. This angle does not depart too far from the 90 degree phase relationship required for perfect circular polarization.

Figures 4 and 5 similarly analyze the radiation in a reference plane which is perpendicular to a plane passing through conductors 11, 31.

In Figure 4 it will be seen that the radiation A1 from conductor II and the radiation As from 'conductor 3| are 180 degrees out of phase due to the conductors being a half wave apart and therefore cancel, as far as this reference line is considered. The effective radiation from A2 which, by the time it has advanced to the reference plane Z1, Z1, has a phase angle of -90 degrees. The amplitude, of course, is equal to the radiation from a single conductor, as is shown by the vector diagram in the lower part of Figure 4.

As shown in Figure 5, the radiation from the horizontal conductor 32 is ineffective in the reference line Z2, Z2. The efiective radiation from conductors l2 and 22 is equal to A12Sin.60 degrees and Azsin.60 degrees. These combine, as shown in the vector diagram in the lower part of Figure 5, to form a resultant R which is equal to 1.225 times the radiation from a single conductor and having a relative phase angle of zero degrees. It will be seen that a perfect phase displacement of 90 degrees exists between the horizontal and vertical radiation along the reference line chosen in this example. The radiation in the vertical members is exactly equal to unity and. that from the horizontal members is only slightly larger than unity so a substantially circular polarization is obtained along this plane.

The analysis of the relationship for the two directions of wave fronts indicated by reference lines X and Z in Figures 2 to 5 are the extreme limits within which the field varies. At any other intermediate direction the resultant field will in amplitude and phase relationship fall somewhere between these two extreme limits. The radiators may be slightly bent or they may be tilted so that even more accurate circular polarization maybe obtained in all directions. Such procedure, however, would be of only slight practical value since the construction shown and described heretofore is sufiiciently accurate for all practical purposes.

While I have shown and particularly described an embodiment of my invention, it is to be definitely understood that my invention is not limited thereto but that modifications within the scope of my invention may be made.

I claim:

1. An antenna comprising a plurality of radiating conductors passing through the corners of a horizontal equilateral triangle havingthe length radiator 32 is efiective in the said direction. The e of its sides equal to a half the length of the opcrating wave, and alternately extending vertically a distance equal toa half the length of the operating wave and horizontally in vertical planes passing through the sides of said triangle where-- by each of said radiating conductors forms a stepped helix about a verticalcenter axis passing 0 through the center of said triangle.

2. An antenna comprising a plurality of radiat ing conductors passing through the corners of a horizontal equilateral triangle having the length of its sides equal to a half the length of the operating wave and alternately extending vertically a distance equal toa half the length of the operat-' ing wave and horizontally in vertical planes passing through the sides of said triangle whereby each of said radiating conductors forms a stepped helix about a supporting mast passing through the center of said triangle.

3. An antenna comprising a plurality of radiating conductors passing through the corners of a horizontal equilateral triangle having the length of its sides equal to a half the length of the operating wave and alternately extending vertically a distance equal to a half the length of the operating wave and horizontally in vertical planes passing through the sides of said triangle whereby each of said radiating conductors forms a stepped r40 helix about a supporting mast passing through the center of said triangle, and supporting arms connected to said mast at'the midpoints of each of said half wave sections.

4. An antenna comprising a plurality of radiathorizontal equilateral triangle having the length of its sides equal to a half the length of the operating wave and alternately extending vertically a distance equal to a half the length of the operating wave and horizontally in vertical planes passing through the sides of said triangle whereby each of said radiating conductorsforms a stepped helix about a supporting mast passing through the center of said triangle, and supporting arms connected to said mast and to the voltage nodes of each of said half wave sections.

5. An antenna comprising a plurality of radiating conductors passing through the corners of a horizontal equilateral triangle having the length mast and to each of said half wave portions.

6. An antenna comprising several groups of vertical radiators each having a length equal to.

a half the length of the operating wave, the radiators of each group being arranged in a common "vertical axis and several groups of horizontal ra- (1 45 ing conductors passing through the corners of a diators each having a length equal to a half the length of the operating wave, each group of horizontal radiators being arranged in a plane pass-- ing through two adjacent vertical axes and means for cophasally energizing all of said radiators.

'7. An antenna comprising several groups of vertical radiators each having a length equal to a half the length of the operating wave, the radiators of each group being arranged in a common vertical axis and several groups of horizontal radiators each having a length equalto a half the length of the operating wave, each group of horizontal radiators being arranged in a plane passing through two adjacent vertical axes, each of the horizontal radiators, forming a connection between one of the vertical radiators in one of said groups of vertical radiators and the next higher vertical radiator in the adjacent group.

8. An antenna comprising several groups of vertical radiators each having a length equal to a half the length of the operating wave, the radiators of each group being arranged in a common vertical axis and several groups of horizontal radiators each having a length equal to a half the length of the operating wave, each group of horizontal radiators being arranged in a plane passing through two adjacent vertical axes, each of the horizontal radiators forming a connection between one of the vertical radiators in one of said groups of vertical radiators and the next higher vertical radiator in the adjacent group, each of said radiators being cophasally energized.

9. An antennacomprising three groups of vertical radiators, each having a length equal to a half the length of the operating wave, the radiators of each group beingarranged in a common vertical axis and three groups of horizontal radiators, each radiator having a length equal to a half the length of the operating wave, each group of horizontal radiators being arranged in a plane passing through two adjacent vertical axis and means for energizing each of said radiators in the half the length of the operating wave, the radiators of each group being arranged on a common vertical axis and three groups of horizontal radiators each having a length equal to a' half the length of the operating wave, each group of hori-.

vertical radiator in the adjacent group, each of saidradiators being cophasally energized.

11. An antenna comprising three groups of vertical radiators, each having a length equal to a half the length of the operating wave, the radiators of each group being arranged on a common vertical axis and three groups of horizontal radiators each having a length equal to a half the length. of the operating wave, eachgroup of horizontal'radiators being arranged in a plane pass ing through two adjacent vertical axes, each of the horizontal radiators forming a connection between one of the verticalradiators in one of said groupsof vertical radiators and the next higher vertical radiator in theadjacent group, each of said radiators being cophasally energized, and supporting means connected to the voltage nodes of each of said radiators.

12. An antenna comprising three groups of vertical radiators, each having a length equal to a halfthe length of the operating Wave, the radiators of each group being arranged on a common vertical axis and'three groups of horizontal radiators each'having a length equal to a half the length of the operating wave, each group of horizontal radiators being arranged in a plane passing through two adjacent vertical axes, each of the horizontal radiators forming a connection between one of the vertical radiators in one of said groups of vertical radiators and the next higher vertical radiator in the adjacent group, each .of

said radiators being cophasally energized, and conductive supporting means connected to the midpoints of each of said radiators.

- NILS E. LINDENBLAD. 

